Buying a used lower unit for a Force '97 90 hp

[Tim Jeffers]

My '97 Force 90 hp outboard prop doesn't engage in forward or reverse. Engine still runs well. Currently looking for used lower unit to replace it. I searched throughout the internet sites and looked on boards, but I cannot find a table or site as to which years(1995 on up?)/hp models(75 to 120?)/makes(Force or Mercury?), I can interchange with my current lower unit. I am looking on eBay for a unit but cannot tell if the ones being sold will fit. Any help is greatly appreciated. Thanks in advance.